Neuromuscular Disorders Flashcards
What is the pathophysiology behind myasthenia gravis?
Autoimmune destruction of of the postsynaptic neuromuscular junction.
Which antibodies are associated with myasthenia gravis?
Serum AChR Antibodies - Present in 80% of generalized myasthenia and 50% ocular.
MuSK
LRP4
What is the most sensitive findings for myasthenia gravis on EMG/NCS?
Single Fibre EMG of the frontal or orbicularis oculi demonstrating enhanced jitter (Sn 95%).
Which EMG finding is the most specific for myasthenia gravis?
Repetitive nerve stimulation demonstrates decrement (90% specific).
What is the preferred treatment for myasthenic crisis?
Plasmaphersis (PLEX) is preferred by consensus opinion.
IVIG 2g/kg over 2-5 days in another option.
Which medication do you need to hold when a patient with myasthenic crisis is intubated?
Hold pyridostigmine when intubated, to prevent excessive airway secretions.
What is the treatment for symptoms in myasthenia gravis?
Pyridostigmine 60 mg PO TID
What disease modifying therapies can be utilized in myasthenia gravis (6)?
(1) Prednisone (lowest effective dose)
(2) Azathioprine
(3) Mycophenolate mofetil
(4) Plasmapheresis (PLEX)
(5) IVIg
(6) Eculizumab
What is the role of thymectomy in myasthenia gravis?
If a thymoma is present (10% of MG patients), refer to thoracic surgery for thymectomy.
If no thymoma, consider elective thymectomy if the patient is young (<60 years), has + AChRAb or the disease duration has been < 5 years.
Which drugs should be avoided in patients with myasthenia gravis (7)?
(1) Anesthetic Agents
(2) Antibiotics - Fluoroquinolones, Macrolides, Aminoglycosides
(3) CV Drugs - B-blockers, procainamide, quinidine
(4) Checkpoint Inhibitors - Anti-PD1 monoclonal ab (pembrolizumab, nivolumab)
(5) Botulinum Toxin
(6) Choroquine, Hydroxychloroquine
(7) Magnesium, Lithium
